A new study suggests people who had certain kinds of dental X-rays in the past may be at an increased risk for meningioma, the most commonly diagnosed brain tumor in the U.S.
The findings cannot prove that radiation from the
imaging caused the tumors, and the results are based on people who were
likely exposed to higher levels of radiation during dental X-rays than
most are today.
"It's likely that the exposure association we're seeing
here is past exposure, and past exposure levels were much higher," said
Dr. Elizabeth Claus, the study's lead author and a professor at the
Yale School of Medicine in New Haven, Connecticut.
Claus and her colleagues write in the journal Cancer
that dental X-rays are the most common source of exposure to ionizing
radiation -- which has been linked to meningiomas in the past -- but
most research on the connection is based on people who were exposed to
atomic bombs or received radiation therapy.
There have been some studies that looked at dental
X-rays, but they were from years ago and included fewer people than the
current study, Claus noted. Still, they were generally in agreement with
the new findings.
For her study, Claus' team recruited 1,433 people
diagnosed with intracranial meningioma -- a tumor that forms in the
tissues lining the brain -- between May 2006 and April 2011. All of the
participants were diagnosed when they were between 20 and 79 years old
and they were all from Connecticut, Massachusetts, North Carolina or the
Houston or San Francisco Bay areas.
For comparison, the researchers also followed 1,350
people who were similar in age, sex and state of residence as the study
group, but who had not been diagnosed with a tumor.
The study looked at how often people had three
different types of dental X-rays. They included a focused image of one
area, a number of images of the full mouth and a single panoramic view
of the entire mouth. These are known in dentistry parlance as bitewing,
full-mouth and panorex films, respectively.
Each person was interviewed by someone trained to
administer a questionnaire that asked about demographic details, family
history of cancer, pregnancy and medical history. The interviewers also
asked -- among other things -- about the person's history of dental work
and the number of times they had the three types of dental x-rays taken
throughout their life.
The researchers found that those diagnosed with
meningiomas were more than twice as likely as the comparison group to
report ever having had bitewing images taken.
And regardless of the age when the bitewings were
taken, those who had them yearly or more frequently were at between 40
percent and 90 percent higher risk at all ages to be diagnosed with a
To put that in perspective, Dr. Paul Pharoah, a cancer
researcher at the University of Cambridge said in a statement the
results would mean an increase in lifetime risk of intracranial
meningioma in the U.K. from 15 out of every 10,000 people to 22 in
Panoramic X-rays taken at a young age, especially if
done yearly or more often before age 10, also raised the risk of
meningiomas by up to five times.
There was no association between full-mouth X-rays and
the tumors, although the authors note they saw a trend similar to that
seen for the bitewing X-rays.
The lack of association with full-mouth X-rays led one expert to question the connection.
"They found a small risk (from) a pair of bitewings,
but not a full mouth series, which is multiple bitewings. That
inconsistency is impossible to understand to me," said Dr. Alan Lurie,
president of the American Academy of Oral and Maxillofacial Radiology.
Lurie also echoed Claus' caution that radiation levels
from dental X-rays when some of the participants were younger was much
greater than is used now.
He does warn, however, patients shouldn't assume it's fine for the dentist to take X-rays.
"They should ask why are (dentists) taking this image and what is the benefit to me," he said.
The American Dental Association put out a statement in
response to the study noting that the interviews relied on participants'
memories of how often they had different types of X-rays years earlier.
The statement added, "The ADA's long-standing position
is that dentists should order dental X-rays for patients only when
necessary for diagnosis and treatment. Since 1989, the ADA has published
recommendations to help dentists ensure that radiation exposure is as
low as reasonably achievable."
Dr. Sanjay Mallya, an assistant professor the UCLA
School of Dentistry in Los Angeles, said that patients should be
concerned whenever they are exposed to radiation, but "it's important to
emphasize that this concern should not mean that we shouldn't get
X-rays at all."
According to the researchers, "while dental X-rays are
an important tool in well selected patients, efforts to moderate
exposure to (ionizing radiation) to the head is likely to be of benefit
to patients and health care providers alike."
(The photo previously attached to the story has been removed.)
SOURCE: http://bit.ly/HwspDv Cancer, online April 10, 2012.
NOTE: It is also recommended that you research side effects of cell phones, cell towers and microwave ovens.